Model-Free Adaptive Frequency Calibration for Voltage-Controlled Oscillators

The operating frequency accuracy of the local oscillators is critical for the overall system performance in the communication systems.However,the high-precision oscillators could be too expensive for civil applications.In this paper,we propose a model-free adaptive frequency calibration framework for a voltage-controlled crystal oscillator(VCO)equipped with a time to digital converter(TDC),which can significantly improve the frequency accuracy of the VCO thus calibrated.The idea is to utilize a high-precision TDC to directly measure the VCO period which is then passed to a model-free method for working frequency calibration.One advantage of this method is that the working frequency calibration employs the system history of input/output(I/O)data,instead of establishing an accurate VCO voltagecontrolled oscillator model.Another advantage is the lightweight calibration method with low complexity such that it can be implemented on an MCU with limited computation capabilities.Experimental results show that the proposed calibration method can improve the frequency accuracy of a VCO from±20 ppm to±10 ppb,which indicates the promise of the modelfree adaptive frequency calibrator for VCOs.

2.7-4.0 GHz PLL with dual-mode auto frequency calibration for navigation system on chip

A 2.7-4.0 GHz dual-mode auto frequency calibration(AFC) fast locking PLL was designed for navigation system on chip(SoC). The SoC was composed of one radio frequency(RF) receiver, one baseband and several system control parts. In the proposed AFC block, both analog and digital modes were designed to complete the AFC process. In analog mode, the analog part sampled and detected the charge pump output tuning voltage, which would give the indicator to digital part to adjust the voltage control oscillator(VCO) capacitor bank. In digital mode, the digital part counted the phase lock loop(PLL) divided clock to judge whether VCO frequency was fast or slow. The analog and digital modes completed the auto frequency calibration function independently by internal switch. By designing a special switching algorithm, the switch of the digital and analog mode could be realized anytime during the lock and unlock detecting process for faster and more stable locking. This chip is fabricated in 0.13 μm RF complementary metal oxide semiconductor(CMOS) process, and the VCO supports the frequency range from 2.7 to 4.0 GHz. Tested 3.96 GHz frequency phase noise is -90 d Bc/Hz@100 k Hz frequency offset and -120 d Bc/Hz@1 MHz frequency offset. By using the analog mode in lock detection and digital mode in unlock detection, tested AFC time is less than 9 μs and the total PLL lock time is less than 19 μs. The SoC acquisition and tracking sensitivity are about-142 d Bm and-155 d Bm, respectively. The area of the proposed PLL is 0.35 mm^2 and the total SoC area is about 9.6 mm^2.

Broadband Frequency Comb for Calibration of Astronomical Spectrographs

We present our state-of-the-art version of a frequency comb for calibration of astronomical spectrographs. The mode spacing of the frequency comb can be designed to match the resolution of a spectrograph. Combined with its excellent accuracy and stability, the spectral coverage of more than 70% of the whole visible spectrum range makes the frequency comb an ideal calibration source. In addition, the new version introduces the automatic start-up function that brings convenience to the astronomers.

Implementation and integration of a systematic DBPM calibration with PLL frequency synthesis and FPGA

Beam current dependence resulted from nonlinearity and asymmetry of the four channels of digital BPM(Beam Position Monitor) processor deteriorates the BPM performance.A systematic solution based on signal source calibration tactics has been carried out to rectify this defect.It is optimized for implementation in FPGA.Mathematical illustrations of the calibration method,hardware and software design and implementation are presented.A signal source circuit using frequency synthesis technique is designed as calibration standard.Data acquisition system using JAVA web technology and Ethernet is introduced.Integrated FPGA implementation code architecture is presented,and experimental test results show that the method implemented in FPGA is feasible.Compared to other methods,our approach can rectify the nonlinearity and asymmetry simultaneously.The whole solution is integrated into the DBPM processor and can be executed online.

A Σ-Δ Fractional-N PLL Frequency Synthesizer with AFC for SRD Applications

A fractional-N frequency synthesizer for 433/868MHz SRD applications is implemented in a 0.3μm CMOS process. A wide-band VCO and an AFC are used to cover the desired bands. A 3bit third order sigma-delta modulator is adopted to reduce the out-band phase noise. The measurements show a VCO tuning range from 1.31 to 1.88GHz with AFC working correctly,an out-band phase noise of -139dBc/Hz at 3MHz offset frequency, and a fractional spur of less than - 60dBc. The chip area is 1.5mm × 1.2mm and the total current dissipation including LO buffers is 19mA from a single 3.0V supply voltage.

A 5-GHz frequency synthesizer with constant bandwidth for low IF ZigBee transceiver applications

A fully integrated integer-N frequency synthesizer is implemented.The synthesizer is designed for low intermediate frequency （IF）ZigBee transceiver applications.Techniques used to make the loop bandwidth constant across the whole output frequency range of the voltage controlled oscillator（VCO）are adopted to maintain phase noise optimization and loop stability.In-phase and quadrature（IQ）signals are generated by a 1/2 frequency divider at the output of the VCO.The synthesizer is fabricated in 0.18 μm radio frequency（RF） complementary metal oxide semiconductor transistor （CMOS）technology.The chip area is 1.7 mm2.The synthesizer is measured on wafer.It consumes totally 28.8 mW excluding output buffers from a supply voltage of 1.8 V.The measured phase noise is -110 and -122 dBc/Hz at the offset of 1 and 3 MHz from a 2.405 GHz carrier,respectively.The measured reference spur at a 2 MHz offset from a 2.405 GHz carrier is-48.2 dBc.The measured setting time of the synthesizer is about 160 μs.

Study of sedimentary sequence cycles by well-seismic calibration

In order to solve the problems of the fine division of sedimentary sequence cycles and their change in two-dimensional space as well as lateral extension contrast, we developed a method of wavelet depth-frequency analysis. The single signal and composite signal of different Milankovitch cycles are obtained by numerical simulation. The simulated composite signal can be separated into single signals of a single frequency cycle. We also develop a well-seismic calibration insertion technology which helps to realize the calibration from the spectrum characteristics of a single well to the seismic profile. And then we determine the change and distribution characteristics of spectrum cycles in the two-dimensional space. It points out the direction in determining the variations of the regional sedimentary sequence cycles, underground strata structure and the contact relationship.

Comparison and error analysis of remotely measured waveheight by high frequency ground wave radar

High frequency ground wave radar （HFGWR） has unique advantage in the survey of dynamical factors, such as sea surface current, sea wave, and sea surface wind in marine conditions in coastal sea area. Compared to marine satellite remote sensing, it involves lower cost, has higher measuring accuracy and spatial resolution and sampling frequency. High frequency ground wave radar is a new land based remote sensing instrument with superior vision and greater application potentials. This paper reviews the development history and application status of high frequency wave radar, introduces its remote-sensing principle and method to inverse offshore fluid, and wave and wind field. Based on the author＇s ＂863 Project＂, this paper recounts comparison and verification of radar remote-sensing value, the physical calibration of radar-measured data and methods to control the quality of radar-sensing data. The authors discuss the precision of radar-sensing data＇s inversing on offshore fluid field and application of the assimilated data on assimilation.

Automated Calibration of RF On-Wafer Probing and Evaluation of Probe Misalignment Effects Using a Desktop Micro-Factory

A fully automatic setup for on-wafer contact probing will be presented. This setup consists of six automatable nano positioning axes used as tool holder and a sample holder. With this setup a fully automatic one-port SOL calibration for a Vector Network Analyzer is done. Furthermore a fully automated on-wafer contact probing is performed. Afterwards, the effects of a misalignment of the three tips of a GSG-probe are examined. Additionally the error on the calibration is calculated to determine its effect on the measurement. The results show, that a misalignment of the probe has a high impact on the measurement of the VNA. Hence a fully automated on-wafer probing presented in this paper is a good way to detect these misalignments and correct them if necessary.

一种基于频差自校准的高精度RC振荡器

提出了一种基于频差自校准的高精度RC振荡器。通过对PTAT高频环形振荡器时钟计数,得到RC振荡器和参考时钟的计数偏差。数字自校准电路通过电阻阵列校准参考电压,减小计数偏差,进而得到稳定的振荡频率。参考时钟仅在工作前校准,实际工作中不需要额外的参考时钟。该RC振荡器采用CSMC 0.18μm工艺,工作电压为1.8 V。仿真结果表明,该电路可以产生2 MHz的稳定振荡频率,整个系统的功耗为48.4μW,启动时间小于15μs。在-40~125℃温度范围内,振荡频率变化率小于±0.2%。在1.70~1.98 V供电电压范围内,振荡频率变化率小于±0.25%/V。

太阳系外行星探测技术概述

自20世纪90年代首次发现太阳系外行星(以下简称系外行星)以来,系外行星探测技术取得了飞速发展。目前已探测到超过5500颗系外行星,其中包括类地行星、超级地球、气态巨行星及冰巨行星等多种类型。这些发现极大地拓展了人类对自身周围环境和宇宙的认知,为理解行星形成和演化提供了宝贵的观测依据,也为寻找宜居行星和地外生命提供了重要线索。通过介绍系外行星探测的多种核心技术,包括原理和应用特点,旨在对比和分析不同探测方法的技术特征。通过分析多种探测技术的优势和局限性,为行星探测研究提供了实践参考和发展趋势展望。

基于SPWM的电磁流量计谐振式励磁系统研制

为了使电磁流量计长期可靠运行,需要降低励磁系统功耗并减少发热。因此,文中提出了一种基于SPWM控制的谐振式电磁流量计励磁控制方案,改变以往的恒流源驱动方式,采用高频开关电压源驱动,同时在励磁回路中串联电容来减少回路阻抗,并研制样机、开展实验验证。功耗测试结果表明:在相同励磁电流的条件下,所研制励磁系统功耗为原系统的58.3%,励磁电源功率为原系统的69.2%。水流量标定结果表明:当励磁频率为109.5 Hz时,所研制系统在水流速为0.5~5 m/s时标定精度满足0.5级要求。可见,所研制的励磁系统具有功耗低、测量精度高的特点。

轨道交通添乘仪双向加速度校准方法的研究

为确保轨道交通行业计量仪器量值准确性和溯源性,为仪器性能评价提供依据及提高行业的质量控制。首先介绍了便携式添乘仪的工作原理,然后建立了基于标准低频振动台和标准低频加速度计测量添乘仪的水平和垂直双方向的加速度校准装置,最后通过试验分析,研究幅值频率响应和幅值线性度及评定了加速度参数的扩展不确定度。试验结果表明,在加速度范围0.02~0.20 g范围,频率范围为2~5 Hz范围内,垂直和水平方向加速度绝对误差在±0.01 g范围内;随着试验频率和加速度的增加,幅值频率响应和幅值线性度的绝对误差随之增加;通过低频加速度校准装置测量添乘仪测量精度高,扩展不确定度为Urel=4.8%(k=2),可根据JJG2054-2015计量检定系统表,将加速度参数溯源到国家基准,实现了轨道交通专用计量仪器量值准确性和溯源性。

数字示波器相频特性的计量评价

针对数字示波器相频特性校准中,响应波形与激励信号之间相位差获取的难点问题,提出一种借助于脉冲沿幅度触发功能特性的方法,通过设定触发参量与激励信号幅度关系,固定与响应信号波形相对应的激励信号的相位点,从而精确获取被测数字示波器的相移特性,并统一了不同频率下相移特性的参考相位点,顺利获得数字示波器相频响应特性曲线。在一组实验中,验证了所述方法的有效性和可行性,可用于数字示波器相频响应特性的测量评价。

船用无线电标校信标机程控频点切换的设计

船用无线电标校信标机是指能够为船载统一测控设备提供稳定跟踪信号的射频信号发生器。一般安装于探空气球内部或悬挂于无人机底部,经过飞行至一定高度和距离后,船载统一测控设备对该信标信号进行跟踪试验。当前船用无线电标校信标机在空中仅能工作在一个频点,若需要对多个工作频点进行标校则需要重复释放多个无线电信标机。为解决此问题,设计一种标校信标机外围变频控制电路,将该电路连接至标校信标机即可完成释放一个信标机开展多频点标校的难题。该变频电路以低功耗单片机STC89C52RC作为基本控制单元,结合DC⁃DC降压模块和电平转换模块,实现将多个预置工作频点信息按预定帧格式定时发送至信标机的功能。经过十余次海上航天测量试验的检验,结果表明程控变频控制电路运行稳定、控制精度高,节省了标校时间和经费预算。

TT-1装置磁探针设计与频响特性研究

利用NI Multisim仿真设计软件对泰国托卡马克1号(TT-1)磁探针的电路仿真模型进行测试,得出了探针的频响特性,其中分布电容主要影响磁探针的谐振频率大小,回路电感对磁探针的谐振频率和谐振峰值均有一定影响。基于亥姆霍兹线圈,进行了探针频响标定实验,结果显示磁探针的频率响应和仿真结果具有较好的一致性。通过实验和数值方法,分析了探针传输线缆长度对探针幅频响应的影响。确定了TT-1装置探针的频响参数,为探针尺寸的设计以及信号传输线缆的选择提供了重要的参考依据。

基于谐振效应的自激振荡脉冲超临界二氧化碳射流最优冲击靶距研究

超临界二氧化碳(SC-CO_(2))射流在钻井工程中具有广泛应用前景,并且其破煤压力阈值低、效率高,能够提高钻井效率。但因其较高的破煤门限压力和系统能耗,限制了其推广应用。自激振荡脉冲SC-CO_(2)射流的高脉冲压力和谐振效应可有效降低破煤门限压力,显著提高破煤效率。基于此,开展了自激振荡脉冲SC-CO_(2)射流脉冲频率和脉冲压力幅值对谐振破煤的综合作用研究。采用大涡模拟分析了射流流场结构,明确了流场轴向上脉冲频率和脉冲压力幅值的变化规律;通过脉冲特征测试实验研究了靶距对射流冲击频率和冲击压力的影响,并通过冲击破煤实验研究了脉冲特征对破煤的综合影响,得到了以下结论:自激振荡脉冲SC-CO_(2)射流脉冲频率和压力幅值在射流轴向处并不会保持不变,随着靶距的不断增大均呈现逐渐减小的趋势。仅考虑脉冲频率并不能将谐振效应最大化,需要综合考虑脉冲频率和压力幅值对谐振效应的影响。采用位移响应振幅表征谐振效果,能够反映频率和幅值对谐振的综合影响。靶距较小时,即0~15 mm,位移响应振幅的主要影响因素为脉冲压力幅值;靶距较大时,即15~30 mm,其主要影响因素转变为脉冲频率。减小脉冲频率并增加压力幅值能够有效提高位移响应振幅。不同喷嘴结构条件下,位移响应振幅主要影响因素的转变位置不同,同时最优靶距也并不相同。该研究中,喷嘴a的最优靶距是22 mm,此处的位移响应振幅最大,破煤效果最好,而喷嘴b的最优靶距是26 mm。

633 nm热稳频He-Ne激光真空波长校准研究

633 nm热稳频He-Ne激光是激光干涉测量技术中应用最广泛的波长标准光源。633 nm激光波长是几何量计量中最重要的溯源路径。该文分析了633 nm热稳频He-Ne激光的频率特性,并以此为依据详细探讨了633 nm热稳频He-Ne激光器真空波长的校准内容和校准方法。在激光平均波长测量和波长不确定度评定中均考虑了波长复现性产生的影响,给出了校准数据处理方法和不确定度评定示例。结果显示,在633 nm热稳频He-Ne激光真空波长校准中,考虑复现性的影响是必要的。

磁电式低频振动传感器原位校准改进型系统的设计与实现

针对拾振器的原位校准在高频段的灵敏度误差大的问题,构建了改进校准电路后系统模型。通过实验,得到原位校准与激光干涉法的归一化灵敏度的相对误差,发现改进电路后的相对误差小于改进电路前的相对误差。此外,在实验过程中,水平向传感器对于安装角度有较高的要求,分别改变传感器与水平面的夹角,获得了激光干涉法与原位校准法的校准结果,发现当传感器与水平面有一定夹角时,使用改进后校准的方法后,低频灵敏度与高频灵敏度的误差变大。

频率—波数域水陆检数据上、下行波场分离方法

随着海洋油气勘探开发的发展,OBC/OBN水陆检海底接收的应用日趋广泛,上、下行波场分离作为水陆检数据处理的关键技术,决定了资料处理品质及应用效果。常规方法分离出来的上行波场中包含下行波场,下行波场中包含上行波场,即不能实现上行波场与下行波场的完全分离。为此,提出在频率—波数域利用包含直达波和切除直达波后的水陆检数据,直接计算水陆检数据标定滤波因子,实现水陆检数据标定和上、下行波场分离。分离后的上行波场数据中既消除了虚反射多次波干扰,又提高了地震数据信噪比和分辨率,为后续联合反褶积和偏移成像等处理提供了高保真的上行波场和下行波场数据。数据实例表明了所提方法的有效性和实用性。